1. Field of the Invention
The present invention relates to a semiconductor device and its manufacturing method and more particularly to a semiconductor device and its manufacturing method wherein the deformation of a groove for interconnection by the compressive stress of a barrier metal layer used for an interconnection in a groove (hereinafter called grooved interconnection) having a single damascene structure or a dual damascene structure is prevented.
2. Description of Related Art
The reduction of the resistance of an interconnection and the reduction of the dielectric constant of an interlayer insulating film are desired to meet requests for the miniaturization and speedup of an LSI device. To meet the desire, a copper interconnection lower in electrical resistance, compared with conventional type aluminum alloy interconnection and various organic insulating films lower in a dielectric constant, compared with a conventional type silicon oxide (SiO2) film are examined for actual use.
For technology for forming a copper interconnection, as the dry etching of copper is generally not easy, a method by a so-called grooved interconnection is considered promising. For technology for forming the grooved interconnection, 1) a method of forming an insulating film between interconnection on an interlayer insulating film after embedding interconnection material in a contact hole formed through the interlayer insulating film and embedding interconnection material in a groove after forming the groove on the insulating film (a so-called single damascene method) and 2) a method of simultaneously embedding interconnection material in both a contact hole and a groove after forming both the contact hole and the groove through/on an interlayer insulating film (a so-called dual damascene method) are proposed.
For a method of embedding copper as an interconnection material in a groove and a contact hole, electroplating relatively satisfactory in embeddability and the quality of a film which is a low-temperature process under approximately room temperature is promising. Particularly, it is advantageous in case organic insulating material low in heat resistance is used for an insulating film that electroplating is a low-temperature process.
In the meantime, copper as an interconnection material has a character diffused inside an insulating film. Therefore, to form a copper grooved interconnection, a barrier metal layer is required to be formed between copper and the insulating film. For a barrier metal, tantalum, titanium nitride and tungsten nitride are promising in addition to tantalum nitride used heretofore.
FIG. 13 shows an example that copper grooved interconnection is formed using organic insulating material. As shown in FIG. 13, an organic insulating material film 112 is formed on a silicon oxide film 111 and a groove 113 is formed on the organic insulating material film 112. Grooved interconnection 115 made of copper is formed inside the groove 113 via a barrier metal layer 114 made of tantalum nitride. When the groove 113 is formed by etching, the silicon oxide film 111 functions as an etching stopper. Therefore, the groove 113 is formed in only the organic insulating material film 112 on the silicon oxide film 111 and the bottom of the groove 113 is on the silicon oxide film 111.
However, as for the grooved interconnection, in case tantalum nitride is used for barrier metal, a problem that the organic insulating material film is deformed by the compressive stress of the tantalum nitride is found. It proves that the deformation is often caused particularly in isolated grooved interconnection or grooved interconnection in close formation (for example, grooved interconnection at the end of a line and space). The reason is that though mechanical strength is weak because organic insulating material is generally small in an elastic modulus and is also low in an elastic limit, barrier metal such as tantalum nitride generally has very high compressive stress.
That is, as shown in FIG. 14A, it is considered that the groove 113 is easily deformed inside because the compressive stress of the barrier metal layer 114 particularly made of tantalum nitride widely deposited in an area having no grooved interconnection concentrates at the corner 113C of the outside groove 113. It is also considered that the deformation of the groove 113 is promoted because adhesion between the organic insulating material film 112 and the silicon oxide film 111 under the organic insulating material film is not sufficient and sliding occurs between the organic insulating material film 112 and the silicon oxide film 111 by stress concentrating at an interface between the organic insulating material film 112 and the silicon oxide film 111.
As shown in FIG. 14B, as a copper seed layer is not fully deposited in the formation of a film by later sputtering in the groove 113 deformed as described above, failure in embedding copper occurs in electroplating for forming the grooved interconnection 115. That is, a void B is made in the grooved interconnection 115.
The present invention is made to solve the problems and the object is to provide a semiconductor device and its manufacturing method respectively free of the problems.
A semiconductor device according to the invention is based upon a semiconductor device having a groove formed through an insulating film made of organic material on a substrate, a barrier metal layer formed on at least the inner wall of the groove and a grooved interconnection embedded inside the groove via the barrier metal layer and is characterized in that a concave portion is formed through an insulating film around the grooved interconnection. The concave portion is continuously or intermittently formed along the groove within a predetermined interval from the groove. Or the groove is arranged at the end of a group of grooves composed of plural grooves respectively arranged at a predetermined interval and the concave portion is continuously or intermittently formed along the groove within a predetermined interval outside the group of grooves from the groove arranged at the end of the group of grooves.
In the semiconductor device, a barrier metal layer is formed on the inner wall of the groove. Normally, it is difficult to selectively form a barrier metal layer only inside a groove formed through an insulating film because of a characteristic in forming a film and the barrier metal layer is formed not only inside the groove but also on the insulating film. Afterward, in a process for forming a grooved interconnection, a surplus barrier metal layer on the insulating film is removed; however, when a concave portion is formed through the insulating film, the barrier metal layer may be left inside the concave portion. In the invention, in such a semiconductor device, as a concave portion is formed through an insulating film around the grooved interconnection, a barrier metal layer is formed not only inside a groove in which the grooved interconnection is formed but also on the surface of the insulating film and inside the concave portion when the barrier metal layer is formed. Therefore, as compressive stress of the barrier metal layer is relaxed by the concave portion and the large compressive stress of the barrier metal layer is not applied to the groove in which the grooved interconnection is formed, the deformation of the groove is inhibited.
Also, in case the barrier metal layer formed on the inner wall of the groove is also formed on the surface of the insulating film, it is inhibited that the large compressive stress of the barrier metal layer concentrates at the groove because the concave portion is continuously or intermittently formed along the groove within a predetermined interval from the groove. For example, if an interval between the concave portion and the groove is approximately within 20 times of the width of the groove, the interval is enough to inhibit the concentration of the compressive stress of the barrier metal layer. Or in case a groove is arranged at the end of a group of grooves composed of plural grooves respectively arranged at a predetermined interval and a concave portion is continuously or intermittently formed along the groove within a predetermined interval outside the group of grooves from the groove arranged at the end of the group of grooves, it is also inhibited as described above that the large compressive stress of a barrier metal layer concentrates at the groove.
A first manufacturing method according to the invention is based upon a method of manufacturing a semiconductor device having a process for forming a groove through an insulating film made of organic material on a substrate, a process for forming a barrier metal layer at least on the inner wall of the groove, a process for embedding conductive material inside the groove via the barrier metal layer and a process for removing surplus conductive material and a surplus barrier metal layer on the insulating film, and is characterized in that when a groove is formed through an insulating film, a concave portion is formed around the groove.
Also, the first manufacturing method according to the invention is characterized in that when the barrier metal layer is formed on the insulating film, the concave portion is continuously or intermittently formed along the groove within a predetermined interval which between the concave portion and the groove keeps the shape of the groove.
Or the first manufacturing method according to the invention is characterized in that a groove is set as the one provided at the end of a group of grooves composed of plural grooves respectively arranged at a predetermined interval and when a barrier metal layer is formed on an insulating film, a concave portion is continuously or intermittently formed along the groove provided at the end of the group of grooves within a predetermined interval which between the concave portion and the groove provided at the end of the group of grooves keeps the shape of the groove provided at the end of the group of grooves.
According to the first manufacturing method, as compressive stress of the barrier metal layer formed on the insulating film is relaxed by the concave portion when afterward, the barrier metal layer is formed because the concave portion is formed around the groove when the groove is formed through the insulating film, the deformation of the groove by the compressive stress of the barrier metal layer is inhibited. As a result, conductive material is satisfactorily embedded without making a void in the groove.
Also, as the concave portion is continuously or intermittently formed along the groove within a predetermined interval which between the concave portion and the groove keeps the shape of the groove when the barrier metal layer is formed on the insulating film, the groove is prevented from being deformed by the compressive stress of the barrier metal layer formed between the groove and the concave portion. In other words, the barrier metal layer between the groove and the concave portion does not have compressive stress enough to deform the groove. Therefore, even if the compressive stress of the barrier metal layer concentrates at the groove, the groove is not deformed. For example, in case an interval between the concave portion and the groove is within 20 times of the width of the groove, normally the compressive stress of the barrier metal layer between them is not enough to deform the groove. The reason is that the compressive stress of the barrier metal layer between the groove and the concave portion is relaxed because compressive stress of the barrier metal layer formed in a large area on the insulating film concentrates at the concave portion. As a result, the deformation of the groove is inhibited. As a further result, conductive material is satisfactorily embedded without making a void in the groove.
In case an interval between the concave portion and the groove exceeds 20 times the width of the groove, the groove is deformed by the compressive stress of the barrier metal layer formed on the insulating film between them. Therefore, an interval between the concave portion and the groove is required to be set within 20 times of the width of the groove.
Or as also in a method of setting a groove as the one provided at the end of a group of grooves composed of plural grooves respectively arranged at a predetermined interval and continuously or intermittently forming a concave portion along the groove at the end of the group of grooves within a predetermined interval which between the concave portion and the groove provided at the end of the group of grooves keeps the shape of the groove at the end of the group of grooves when a barrier metal layer is formed on an insulating film, the barrier metal layer between the groove at the end and the concave portion does not have compressive stress enough to deform the groove at the end, the groove at the end is never deformed even if the compressive stress of the barrier metal layer concentrates at the groove at the end. For example, in case an interval between the concave portion and the groove at the end is within 20 times of the width of the groove, normally the compressive stress of the barrier metal layer between them is not enough to deform the groove at the end. The reason is that the compressive stress of the barrier metal layer between the groove at the end and the concave portion is relaxed because compressive stress of the barrier metal layer formed in a large area on a second insulating film concentrates at the concave portion and as a result, the deformation of the groove at the end is inhibited. As a result, conductive material is satisfactorily embedded without making a void in the groove at the end.
A second manufacturing method according to the invention is based upon a method of manufacturing a semiconductor device having a process for forming a first insulating film on a substrate, a process for forming a contact hole through the first insulating film, a process for forming a second insulating film made of organic material on the first insulating film, embedding the organic material in the contact hole, a process for forming a groove through the second insulating film and forming a contact hole again, a process for forming a barrier metal layer at least on each inner wall of the groove and the contact hole, a process for embedding conductive material inside the groove and the contact hole via the barrier metal layer and a process for removing surplus conductive material on the second insulating film and a surplus barrier metal layer, and is characterized in that when a contact hole is formed through a first insulating film, a first concave portion is formed through the first insulating film in a position apart by predetermined distance from the contact hole around a part located under a groove formed through a second insulating film and when the second insulating film is formed, a second concave portion is formed on the surface of the second insulating film on the first concave portion.
Also, the second manufacturing method according to the invention is characterized in that when a barrier metal layer is formed on the second insulating film, the second concave portion is continuously or intermittently formed along the groove within a predetermined interval which between the second concave portion and the groove keeps the shape of the groove.
The second manufacturing method according to the invention is characterized in that a groove is set as the one provided at the end of a group of grooves composed of plural grooves respectively arranged at a predetermined interval. When the barrier metal layer is formed on the second insulating film, the second concave portion is continuously or intermittently formed along the groove arranged at the end of the group of grooves within a predetermined interval which between the second concave portion and the groove provided at the end of the group of grooves keeps the shape of the groove provided at the end of the group of grooves.
According to the second manufacturing method, as the first concave portion is formed through the first insulating film in a position apart from the contact hole by predetermined distance around a part located under the groove formed through the second insulating film when the contact hole is formed through the first insulating film and the second concave portion is formed on the surface of the second insulating film on the first concave portion when the second insulating film is formed, compressive stress of the barrier metal layer is relaxed by the second concave portion when afterward, the barrier metal layer is formed and it is inhibited that the groove is deformed by the compressive stress of the barrier metal layer. As a result, conductive material is satisfactorily embedded without making a void in the groove.
Also, as the second concave portion is continuously or intermittently formed along the groove within a predetermined interval which between the second concave portion and the groove keeps the shape of the groove when the barrier metal layer is formed on the second insulating film, the groove is not deformed with the compressive stress of the barrier metal layer formed between the groove and the second concave portion. In other words, the barrier metal layer between the groove and the second concave portion does not have compressive stress enough to deform the groove. Therefore, even if the compressive stress of the barrier metal layer concentrates at the groove, the groove is not deformed. For example, in case an interval between the second concave portion and the groove is within 20 times of the width of the groove, normally the compressive stress of the barrier metal layer between them is not enough to deform the groove. The reason is that as compressive stress of the barrier metal layer formed in a large area on the second insulating film concentrates at the second concave portion, the compressive stress of the barrier metal layer between the groove the concave portion is relaxed and as a result, the deformation of the groove is inhibited. As a result, conductive material is satisfactorily embedded without making a void in the groove.
As also in a method of setting a groove as the one provided at the end of a group of grooves composed of plural grooves respectively arranged at a predetermined interval and continuously or intermittently forming a second concave portion along the groove at the end of the group of grooves within a predetermined interval which between the concave portion and the groove provided at the end of the group of grooves keeps the shape of the groove at the end of the group of grooves when a barrier metal layer is formed on a second insulating film, the barrier metal layer between the groove at the end and the second concave portion does not have compressive stress enough to deform the groove at the end, the groove at the end is never deformed even if the compressive stress of the barrier metal layer concentrates at the groove at the end. For example, in case an interval between the second concave portion and the groove at the end is within 20 times of the width of the groove, normally the compressive stress of the barrier metal layer between them is not enough to deform the groove at the end. The reason is that the compressive stress of the barrier metal layer between the groove at the end and the second concave portion is relaxed because compressive stress of the barrier metal layer concentrates at the second concave portion and as a result, the deformation of the groove at the end is inhibited. As a result, conductive material is satisfactorily embedded without making a void in the groove at the end.
In case an interval between the second concave portion and the groove at the end exceeds 20 times of the width of the groove, the groove at the end is deformed by compressive stress of the barrier metal layer formed on the second insulating film between the second concave portion and the groove at the end. Therefore, an interval between the second concave portion and the groove at the end is required to be within 20 times of the width of the groove.